Low-Temperature Raman Spectra of l-Histidine Crystals |
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| Authors: | G. P. De Sousa P. T. C. Freire J. Mendes Filho F. E. A. Melo C. L. Lima |
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| Affiliation: | 1. Departamento de Física, Universidade Federal do Ceará, Campus do Pici, C.P. 6030, Fortaleza, 60455-760, Brazil
2. Departamento de Física, Campus Ministro Petr?nio Portella, Universidade Federal do Piauí, 64049-550, Teresina, PI, Brazil
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| Abstract: | We present a Raman spectroscopy investigation of the vibrational properties of l-histidine crystals at low temperatures. The temperature dependence of the spectra show discontinuities at 165 K, which we identify with modifications in the bonds associated to both the NH3 + and CO2 ? motifs indicative of a conformational phase transition that changes the intermolecular bonds. Additional evidence of such a phase transition is provided by differential scanning calorimetry measurements, which identified an enthalpic anomaly at ～165 K. |
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